From: "H. Peter Anvin" <hpa@zytor•com>
To: Ben Hutchings <bhutchings@solarflare•com>
Cc: Thomas Gleixner <tglx@linutronix•de>,
Ingo Molnar <mingo@redhat•com>,
netdev@vger•kernel.org, linux-net-drivers@solarflare•com,
x86@kernel•org
Subject: Re: [PATCH 0/3] x86_64, sfc: 128-bit memory-mapped I/O
Date: Tue, 21 Aug 2012 19:31:24 -0700 [thread overview]
Message-ID: <5034447C.3020203@zytor.com> (raw)
In-Reply-To: <1345601423.2659.100.camel@bwh-desktop.uk.solarflarecom.com>
On 08/21/2012 07:10 PM, Ben Hutchings wrote:
>>
>> Yes, you have to make sure you properly enforce the necessary ordering
>> requirements manually (I think you can do that with sfence).
>
> We did put an sfence after the writes to each register. But some
> systems only want to combine writes that cover an entire cache line, and
> the writes covering a 128-bit register get broken back up into multiple
> writes at the PCIe level. And on some systems these are sent in
> decreasing address order, which breaks the rules for writing to
> TX_DESC_UPD.
>
> To avoid this we'd have to put an sfence in between the writes to a
> register, leaving us back where we started.
>
You realize the same applies to 128-bit writes, right? Some cores
and/or systems will break them up.
-hpa
prev parent reply other threads:[~2012-08-22 2:31 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-22 1:17 [PATCH 0/3] x86_64, sfc: 128-bit memory-mapped I/O Ben Hutchings
2012-08-22 1:20 ` [PATCH 1/3] x86_64: Define 128-bit types for kernel code only Ben Hutchings
2012-08-22 1:23 ` [PATCH 2/3] x86_64: Define 128-bit memory-mapped I/O operations Ben Hutchings
2012-08-22 1:37 ` H. Peter Anvin
2012-08-22 2:04 ` Ben Hutchings
2012-08-22 2:34 ` David Miller
2012-08-22 3:24 ` H. Peter Anvin
2012-08-22 3:29 ` David Miller
2012-08-22 3:49 ` H. Peter Anvin
2012-08-22 3:52 ` Linus Torvalds
2012-08-22 3:59 ` H. Peter Anvin
2012-08-22 4:14 ` David Miller
2012-08-22 21:14 ` David Miller
2012-08-22 21:28 ` Linus Torvalds
2012-08-22 21:38 ` David Miller
2012-08-22 4:35 ` Linus Torvalds
2012-08-22 5:00 ` David Miller
2012-08-22 14:06 ` Linus Torvalds
2012-08-22 4:42 ` Linus Torvalds
2012-08-22 13:26 ` Ben Hutchings
2012-08-22 14:20 ` Linus Torvalds
2012-08-22 14:24 ` Ben Hutchings
2012-08-22 14:30 ` Benjamin LaHaise
2012-08-22 14:58 ` Ben Hutchings
2012-08-22 15:13 ` H. Peter Anvin
2012-08-22 15:27 ` David Laight
2012-08-22 15:49 ` H. Peter Anvin
2012-08-22 15:51 ` Ben Hutchings
2012-08-22 15:54 ` H. Peter Anvin
2012-08-22 16:44 ` Ben Hutchings
2012-08-22 16:49 ` H. Peter Anvin
2012-08-22 16:55 ` Linus Torvalds
2012-08-22 17:09 ` Ben Hutchings
2012-08-22 17:12 ` H. Peter Anvin
2012-08-22 17:27 ` Ben Hutchings
2012-08-22 17:54 ` Linus Torvalds
2012-08-22 18:11 ` Ben Hutchings
2012-08-22 18:18 ` H. Peter Anvin
2012-08-22 18:28 ` Linus Torvalds
2012-08-22 19:01 ` Ben Hutchings
2012-08-22 17:26 ` Linus Torvalds
2012-08-22 16:51 ` Linus Torvalds
2012-08-22 16:59 ` H. Peter Anvin
2012-08-22 15:51 ` H. Peter Anvin
2012-08-22 14:50 ` Linus Torvalds
2012-08-22 14:56 ` Linus Torvalds
2012-08-22 15:05 ` David Laight
2012-08-22 15:16 ` Linus Torvalds
2012-08-22 15:41 ` Ben Hutchings
2012-08-22 14:42 ` David Laight
2012-08-22 1:26 ` [PATCH 3/3] sfc: Use __raw_writeo() to perform TX descriptor push where possible Ben Hutchings
2012-08-22 1:38 ` [PATCH 0/3] x86_64, sfc: 128-bit memory-mapped I/O H. Peter Anvin
2012-08-22 1:43 ` Ben Hutchings
2012-08-22 1:59 ` H. Peter Anvin
2012-08-22 2:10 ` Ben Hutchings
2012-08-22 2:31 ` H. Peter Anvin [this message]
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